Awkward, anxious and prone to daydreaming as an escape from her troubles, Trudy Erskine has never felt like she belongs anywhere. Anywhere, that is, except Glencarragh.

Spending magical summers on Glencarragh with her Aunt Calla were the only thing to shelter her from an otherwise tormented childhood. Until one year when Trudy does the very thing that Aunt Calla has warned her against - she makes a bargain with a faery.

Years later, when a job opens up as an elementary school teaching assistant on her beloved island Trudy knows she has to take it and for the first time she begins to feel settled. She loves her work and she's found warm friendships in Frances and Cliona who accept her strange, daydreaming ways without question.

However, life on the island quickly turns into more than she bargained for.

When Trudy stumbles across a selkie boy, she discovers that all of her daydreams have been real - she has the rare ability to travel between Faery and the mortal realm, to a place called the In-Between. To make the situation more confusing, now that she's come back to Glencarragh, the oath she made years ago is being called in by none other than Skelly, an exiled lord of the sea.

What Skelly wants Trudy to do would mean sacrificing her life as she knows it. But, when you make a promise to a faery, do you have any choice but to follow through on it? Will Trudy be forced to live up to her end of the bargain? Or can she work with her new friends to find an alternative? And what about Lira, the vengeful sea-queen who is bent on taking what's owed to her?

In this exciting conclusion to the Sea Glass Trilogy, return to Glencarragh - to old friends and new - for a tale of hope and magic, where one young woman's desire to escape her worries takes an unexpected turn.